1. Field of the Invention
The present invention is related with a tracking apparatus for an optical disk, and more particularly, it is related with a tracking apparatus, which makes a light beam follow a pit array of the optical disk.
2. Description of the Related Art
An optical disk player, for example, a laser disk (LD) player, reads information recorded on a LD by irradiating a light beam to the LD and receiving the reflected light which is modulated by the LD.
The light beam is made to follow the pit array in case of optically reading the pit array on the disk in the above-mentioned LD player, so that a tracking control is performed.
In this tracking control, a tracking error signal is generated on the basis of the reflected light from the disk. The light beam is made to follow the pit array at a zero-crossing point when the polarity of the tracking error signal changes from minus (-) to plus (+) (or when the polarity of the tracking error signal changes from plus (+) to minus (-), depending on the polarity characteristic of the tracking error signal generating circuit).
In an ordinary LD to which the information is recorded beforehand, the intensity of the reflected light is low at the pit array of the disk, while the intensity of the reflected light is high between the pit arrays of the disk. Accordingly, it becomes possible to make the light beam follow the pit array at the zero-crossing point when the tracking error signal changes from minus (-) to plus (+), as mentioned above.
Apart from that, there is a recordable LD (it is referred as a R-LD, hereinbelow), to which recording is arbitrarily enabled according to a demand of a user. In the R-LD in which the phthalocyanine dye, for example, is used as a recording layer, the intensity of the reflected light is high at the pit array of the disk, while the intensity of the reflected light is low between the pit arrays of the disk, on the contrary to the aforementioned ordinary LD. Thus, the light beam cannot be made to follow the pit array at the zero crossing point when the tracking error signal changes from minus (-) to plus (+). But, it is necessary to make the light beam follow the pit array at the zero crossing point when the tracking error signal changes from plus (+) to minus (-).
In this manner, the tracking polarity at the time of tracking control of this R-LD type is reverse to that of the ordinary LD. Consequently, there is a problem that the R-LD cannot be reproduced by a player for the ordinary LD. Instead, the R-LD requires an exclusive player to deal with the reverse tracking polarity.